It's not necessary to come up with a new spell for this purpose at all; Sunburst destroys a vampire outright, and it's already an 8th level spell for sorcerors.
To quote the SRD:
"An undead creature caught within the globe takes 1d6 points of damage per caster level (maximum 25d6), or half...
That's not to mention the fact that rangers are divine casters too, and that niche may need filling afterwards.
Although, if you *do* decide to strictly eliminate all divine casters... that just means bards are going to be that much more popular.:)